20th Century Boys, Eden: It's an Endless World! Recommendations
Both are about surviving almost extinction due to several reasons, and how society changes and adapts to it. Furthermore, both are also about groups of people unraveling the mysteries surrounding the events of their almost extinction. In both manga we witness the growth of the different characters over long periods of time.
Both manga are plot-oriented, meaning that the scenario is very well developped, with many characters, and covers a long period of time. Both tackle large-scale concerns such as the survival of humanity. That being said, Eden is way more violent than 20th Century Boys, which in return is maybe less realistic and more "rule of cool"